The present invention relates generally to a fastening device for fastening bolts, nuts and the like.
Fasteners such as bolts and nuts are known. When the nut is tightened by means of torque, the bolt has a tendency to move along with the nut, while the reaction force applied by a torque power tool to a nearby stationary object applies a side load to the fastener to be tightened. The thread friction between a bolt and nut, is such, that it has the tendency to drag not firmly connected bolts along where the nut is torqued. In other words, the turning friction created by the nut to be turned in the bolt thread is at times greater than the turning friction of a counter-nut connected to the bolt on the other side of the parts to be connected, despite the fact that a turning counter-nut is subject to facial friction. Even if there is a washer underneath the nut to be turned, it too can drag along while the nut is turned.
When a bolt is threaded into a blind hole in the bottom part of the parts to be connected, it too has a tendency to turn along. For the above reasons, industry applies backup wrenches which stop the bottom nut from turning along or Allen keys that insert into a female hex on top of the blind stud to hold the stud from turning inside the threaded blind hole. This procedure is not always successful as the holding force varies with peak torque requirements resulting from flaws in the bolt thread. However, if it works on occasion or if the other bolt end is sturdly connected, then torsion builds up in the bolt shank apart from the side load created by reacting against the stationary object located distant from the bolt axis. On long bolts this can result in a loss of torque when the bolt unwinds. Thus, the turning of the bolt along with the nut, the built up of bolt torsion and the side load applied is non-desirable. It is therefore necessary to find a way to contravene the turning friction of the nut to be turned and the side load in such a way that the bolt remains stationary and the free bolt shank does not see any torsion or side load. As the side load is created through an offset reaction, the reaction force needs to become coaxial with the action force. This was accompanied by increasing the bolt turning friction relative to the nut turning friction so that the bolt member with its associated parts can be used as a stationary object. As the turning friction of the nut is shared between the threaded engagement with the bolt and the facial engagement with the parts to be connected or the washer, the turning friction of the bolt needs also to be shared. A bolt threaded into a blind hole or connected with a counter nut has one threaded friction there and another one where the bolt is connected with the nut to be turned. As the bearing face friction of the nut usually exceeds the threaded friction on the bottom end of the bolt, the bolt has a tendency to turn along where the nut is torqued. If a turning force is applied to a nut and an opposite and equal turning force is applied to a bolt, either one ends up turning. Therefore, it is necessary to either increase the bolt turning friction or to decrease the nut turning friction, so that when two equal but opposite forces are applied to the bolt and the nut, only the nut turns. This task was accomplished by making the turning friction of the bolt rod subject to the turning friction of the washer. Yet, this by itself does not mean anything because if a turning force is only applied to the nut, the bolt and the washer still can turn along and a side load is still applied to the bolt. It requires in addition a tool, which has an action force and an equal but opposite reaction force such as a torque power tool to guarantee that only the nut turns. By applying a torque power tool to the fastener in such a way that the turning force of the torque power tool in one direction is exerted to the nut and the equal but opposite turning force of the torque power tool is exerted to the bolt rod and the washer, only the nut turns.
A fastener is known in the art, such as for example the fastener disclosed my U.S. Pat. No. 5,318,397. It however has the disadvantage that the inner sleeve needs to be relatively radially thick at the point where it is connected to the washer, as the holding force applicable to the inner sleeve is transferred by the inner sleeve to the washer. Therefore, this connection can see in some instances the entire, opposite turning force applied to the outer sleeve. In addition, a fastener described in my previous patent is costly to produce.
Accordingly, it is an object of present invention to provide a fastening device which avoids the disadvantages of the prior art.
In keeping with these objects and with others which will become apparent herienafter, one feature of present invention resides briefly stated, in a fastening device which has a bolt member, a nut to be turned, and a torque power tool operative for applying a torque to the bolt member and torque to the nut to be turned simultaneously, so that during tightening of the fastener and turning of the nut, the bolt member does not turn or twist due to torsion or side load, the bolt member including a rod and a washer having an axis, the rod having two portions located substantially at is ends, one of the portions being a threaded portion and located at one of the ends to connect with the nut to be turned while another of the portion located at the other of the ends of the rod is adapted to connect with an object at the other end, the washer having two opposite bearing faces extending substantially perpendicular to said axis and being subjected to turning friction, the bearing faces including an upper bearing face adapted to cooperate with a bearing face of the nut to be turned and a lower bearing face adapted to cooperate with a bearing face of one of the two parts, the torque power tool having first drive means connectable with the bolt member to apply a torque to the one portion of the rod and to the washer in one direction, and second drive means connectable with the nut to be turned to apply an equal force in an opposite direction, so that during operation of the torque power tool a turning friction of the washer is added to a turning friction of the one portion of the rod, so that the nut to be turned turns while the bolt member remains stationary.
When the fastening device is designed in accordance with the present invention and includes the bolt member, the nut and the torque power tool as defined hereinabove, it eliminates turning of the bolt or of the washer along with turning of the nut.
In the inventive fastening device including the bolt member, the nut and the torque power tool, the tool when applied will eliminate that the bolt twists in its free shank due to torsion. With the fastening device in accordance with the present invention, including the bolt member and the torque power tool, the usual side load resulting from torque is eliminated.
When the fastener including the bolt and the nut is being tightened by means of the tool, the friction of the bolt relative to the friction of the nut changes. Also, the changed friction of the bolt is kept at all times in the same relation to the friction of the nut, even when the friction of the nut becomes temporarily greater due to kinks in the thread or other discrepancies.
With the inventive fastening device, the turning friction between the nut and the bolt is brought closer and it is possible to use standard commercial parts. A smaller diameter and a less expensive construction is feasible.
The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.